Longitudinal data were collected at four phases of family development: (1) preparental; (2) neonatal; (3) mother-infant; and (4) preschool. Three analyses are reported. The first involves continuity between neonatal and 3-month infant behavior. Few significant associations were found. There is some continuity for males, but not for females. The second analysis concerns endogenous and exogenous contributors to vocal behavior. Findings suggest that males exhibit endogenous continuity, while females are more responsive to environmental (exogenous) influences. Antecedents of preschool activity, examined in the third analysis, were found for males, suggestive of endogenous continuity.